Patent Document 1 describes a nitride semiconductor laser. The nitride semiconductor laser has an active layer to emit light a wavelength of in the ultraviolet region of not more than 375 nm. This active layer is formed on a GaN substrate. The active layer of the nitride semiconductor laser is disposed between a lower cladding layer and an upper cladding layer. At least one of the lower cladding layer and the upper cladding layer includes an AlInGaN layer and an AlGaN layer.